Spatial and Temporal Population Genetics at Deep-Sea Hydrothermal Vents along the East Pacific Rise and Galápagos Rift

Abigail J. Fusaro, Ph.D., 2008 Timothy Shank, Advisor

Ecological processes at deep-sea hydrothermal vents on fast-spreading mid-ocean ridges are punctuated by frequent physical disturbance. Larval dispersal among disjunct vent sites facilitates the persistence of sessile invertebrate species in these geologically and chemically dynamic habitats despite local extinction events. Regional population extension and rapid recolonization by the siboglinid tubeworm Riftia pachyptila have been well documented along the East Pacific Rise and the Galápagos Rift. To increase resolution of population genetic connectivity in time and space, a suite of 12 microsatellite DNA markers were developed for this species. Eight of these loci were used to assess the genetic structure of recent colonists and resident adults collected from nine sites in the eastern Pacific Ocean over a period of seven years, spanning a major seafloor eruption. Results support the existence of population genetic stability through time and small but significant regional genetic structure, largely consistent with major geologic features. Local larval retention is proposed as the primary mechanism maintaining genetic connectivity on ecologically relevant time scales in this patchily distributed species. This thesis broadens the application of recently developed molecular techniques to study the effect of ridge-crest processes and offers new perspectives into marine dispersal, gene flow, and population differentiation.